In recent years, importance of CPR (Cardio-Pulmonary Resuscitation) attracts attention. The term CPR means a method of resuscitating cardiopulmonary function when a sick or wounded person suffers from cardiopulmonary arrest or near-cardiopulmonary arrest. Specifically, there are artificial respiration, cardiac massage on the basis of chest compression (hereinafter, referred to simply as “chest compression”), and defibrillation of heart using AED (Automated External Defibrillator).
In order that the human brain having 10 billion or more brain cells pursue normal activities, a large amount of oxygen is required. Cessation of the oxygen supply to the brain continuing for four minutes or more causes a large number of brain cells to be destroyed, and leads to serious brain damage even though the life of the sick or injured person is maintained. Therefore, CPR which resuscitates cardiopulmonary function and causes the oxygen supply to the brain to restart as soon as possible is very important for the sick or injured person suffering from the cardiopulmonary arrest.
Here, we focus chest compression from among a plurality of detailed methods in CPR described above. There are some important points in chest compression. One of these points is that the chest is sufficiently released every time immediately after the compression by the both hands of a compressing person (the person who performs the chest compression). If this release is not sufficient, insufficient blood circulation may result. For example, in the technology of Patent Literature 1, as regards the chest compression in CPR, whether or not the chest is sufficiently released is determined by comparing outputs from a power sensor or an acceleration sensor and predetermined threshold values.
Another important point relating to the chest compression is that the compression depth is adequate. As regards the compression depth, authorities concerned in Japan and overseas provide a range from 3.8 to 5.1 cm as appropriate if the sick or injured person is adult. If the compression depth is too small, massage effects on the heart is too weak. In contrast, if the compression depth is too large, damage of breastbone or the like may result.